I can second GP.

I have always heard and used authz and authn (pronounced auth-z and auth-n). Bare "auth" typically was used to mean both, but IAM was more clear for that in specific contexts. E.G. you might say someone "authed" to indicate both authentication and authorization, and you might have an IAM team that handles both authentication and authorization.

FWIW, I lead an IAM team.

The distinction was already present in Apache2 configs in early 2000's, although there authentication was "auth", and "authorisation" was authz.

Real travesty came from OAuth. A system designed to handle authorisation was named after the term for authentication.

you're not alone.